Fluorescent light starting and operating circuit with heater and light sensitive cut-out therefor



May 7, 1968 E. 1.. SCHIAVONE 3,

FLUORESCENT LIGHT STARTING AND OPERATING CIRCUIT WITH HEATER AND LIGHT SENSITIVE CUT-OUT THEREFOR Filed Oct. 11, 1965 Fig. I

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United States Patent 3,382,406 FLUURESCENT LIGHT STARTING AND OPERAT- ING CIRCUIT WITH HEATER AND LIGHT SEN- SITIVE CUT-OUT THEREFOR Edward L. Schiavone, 10502 Insley St, Silver Spring, Md. 20902 Filed Oct. 11, 1965, Ser. No. 494,639 8 Claims. (Cl. 315-94) ABSTRACT 6F THE DISCLOSURE A fluorescent lamp having a starter electrode positioned adjacent an operating electrode is connected to the second electrode through a light sensitive means responsive to the light from the lamp for isolating the starter electrode from the lamp circuit.

This invention relates to illuminating systems and more particularly to illuminating systems employing fluorescent lam s.

Pgesently four types of fluorescent lamps are available on the market. The different types are related to their respective operating circuits and are classified as (1) Hot Cathode, Pre-heat Starting (2) Hot Cathode, Instant Starting (3) Cold Cathode (4) RF Lamps. All of these lamps are mercury vapor lamps containing mercury vapor at a relatively low pressure. Preferably, the inner wall of the fluorescent tube is coated with a suitable fluorescent substance to convert the ultraviolet radiation to visible light. Each of these types of lamps requires a suitable starting or ballast circuit to produce the required ionization of the mercury vapor so that the mercury vapor may be sufficiently conductive to conduct electrical current between operating electrodes on opposite terminal ends of the tube. The ballast circuits generally are relatively bulky. For example, in the instance of relatively small lamps of the fluorescent type the ballast must be located in the base of the lamp. Further, these ballast circuits or starting circuits are relatively expensive. Still further, these ballast circuits and the incidental starting portions of the lamp often employ bi-metallic heat responsive relays which are subject to malfunction.

Accordingly, it is an object of this invention to provide an improved fluorescent lamp system including an improved starting circuit.

Another object of this invention is to produce an improved fluorescent starting circuit, all the elements of which are located within the lamp.

Yet another object of this invention is to provide a fluorescent lamp starting circuit which is reliable in operation because it depends upon the light energy rather than heat generated in a circuit and therefore assures proper ionization of the gas within the tube.

A still further object of this invention is to provide a starting circuit within a fluorescent lamp, which starting circuit is de-energized by incident light energy generated within the lamp.

Briefly in accordance with aspects of this invention, I have discovered that a photo-electric switch can be employed in the starting circuit of a fluorescent lamp and mounted within the lamp to etfectively open the starting circuit in response to incident light energy as soon as the gas in the tube is sufliciently ionized to conduct current from its terminal electrodes. Advantageously I employ a photo-electric material having a positive co-eflicient of resistance in that the resistance of the material increases with increased incident radiant energy. One example of such a substance is molybdenite or MoS This material has a positive co-eflicient of resistance to incident radiant energy, having wave lengths less than 6,500 A. Ad-

vantageously, this material is particularly suitable for use in mercury vapor lamps in which the maximum proportron of the energy is Within the resonant spectra of mercury vapor and is concentrated in the range of 4,000 A. to 1,000 A.

In accordance with yet other aspects of this inventron, one embodiment employs a photo-responsive device in one endwall of the tube to effectively disconnect the starting circuit upon the generation of suflicient light energy. In accordance with another embodiment of the invention, photo-electric elements are mounted in each endwall of a fluorescent lamp, effectively to disconnect the starting circuit from both ends of the main circuit.

These and various objects, features and advantages of the invention will be more clearly understood from a reading of the detailed description of the invention in conjunction with the drawing in which:

FIGURE 1 is a view in elevation, partly in section, of one illustrative embodiment of fluorescent lamp system according to this invention;

FIGURE 2 is a view taken along the line 22 of FIGURE 1;

FIGURE 3 is a schematic presentation of the system of FIGURE 1; and

FIGURES 4 and 5 are schematic representations of illustrative embodiments of this invention.

The embodiment of fluorescent system shown in FIG- URE 1 includes a fluorescent lamp 10 which is connected to a source of alternating current energy 12 by means of a conventional line including conductors 13, 14 and a switch 15. The lamp 10 includes a glass tube 16 in which are inserted endwalls 18, 2-0. The endwalls 18, 20 are of insulating material and are sealed to the glass 16 in a manner well known in the art, and are suitably enclosed by means of metal caps 22, 23 respectively, in a manner well known in the art. The endwall 18 supports an electrode 25 positioned transversely of the tube 16 and preferably circular in plan by means of a suitable connecting pin 26. Connecting pin 26 is connected to the switch 15 by means of a conductor 27. The electrode 25 includes an electrically-heated cathode portion 30 connected to a second connecting pin 29 for the purpose of pre-heat starting in a manner well known in the art. The endwall 20 supports a generally cylindrical electrode 32 by means of a pin 33 which pin is connected to the generator 12 by the conductor 13. The electrode 32 has a generally cylindrical skirt portion 34 which is adjacent a semi-cylindrical plate 35 such that the plate 35 and the skirt portion 34 act as opposing plates of acapacitor. The plate 35 is supported on a suitable pin 36 projecting from the endwall 20 and the pin 36 is connected by means of a conductor 37 and a flat, light reactive resistance ring 38 which has a positive coefficient of photo-conductivity which will be subsequently described in detail. The opposite side of the light-reactive member 38 is connected to a pin 40 and the pin 40 is connected to the pin 29 by a suitable conductor 42. Alternatively the conductor 42 may be located entirely within the envelope or tube 1.6 as indicated at 42. If the conductor is located within the tube 16 then it is preferably formed of some suitable transparent conducting material such as zinc sulphate. The starting circuit of this embodiment includes the cathode 30, pin 29, conductor 42, pin 40, photo-sensitive ring 38, capacitor plate 35 and conductor 37.

The tube 16 is filled with mercury vapor in a manner well known in the art and radiates or emits primarily ultraviolet light energy in the region of 1,000 to 4,000 A. The light reactive resistance 38 has a positive coefficient of resistance to the light in the ultraviolet region in that its resistance increases in proportion to the incident light. In other words, when the light or lamp 10 is in the dark or extinguished condition the light-sensitive resistance 38 presents a relatively low resistance to the flow of electrical current. If, however, the tube or light or lamp is ignited and the mercury vapor emits light in accordance with its known type of emission having a maximum emission in the resonance line of 2537 A. then this radiant energy will cause the resistance 38 rapidly to increase such that the resistance effectively opens the circuit between the capacitor plate 35 and the terminal pin 40. One particular example of photo-sensitive material having a positive co-eflicient is moly-bdenite which is a sulfide of molybdenum, M08 This material in addition to having the property of increasing in resistance in response to ultraviolet rays and all radiation above 6,500 A. also has the property of acting somewhat as a rectifier in that it offers a lower resistance to current of one polarity than to the current of the opposite polarity. The photo-resistive and other electrical properties are described in greater detailin Coblentz US. Patent 1,418,- 362 issued June 6, 1922. As best seen in FIGURE 2, the ring of M08 is bounded by concentric circular conductors 39, 41 so that the molybdenite conducts current which is equally distributed throughout its area. Thus the equivalent resistance for any level of incident radiant energy is a function of the volume of molybdenite between concentric conductors .39, 41. r

The operation of the system of FIGURE 1 will now be described in conjunction with the schematic drawing of FIGURE 3 which is a schematic representation of the system of FIGURE 1. In FIGURE 3, the lamp 10 is represented generally in dotted outline and it is understood that a suitable gas, suchas mercury fills the tube between the electrodes 25 and 32. When the switch is closed, electrical current from the generator 12 flows along conductors I4 and 27 to the electrode and similarly flows through the conductor 13 to theelectrode 32. This, however, is not at a sufiicient potential to ionize the mercury vapor between the electrodes 25 and 32 to produce current flow along this path. Accordingly, the lamp does not emit light energy at this time. The alternating current, however, flows through the pre-heat starting cathode through the conductor42 to the photosensitive material 38 which is indicated by a resistor 38a and a serially connected rectifier 38b. The rectifier 38b is merely indicative of the rectifying properties of the photo-sensitive molybdenite 38 while the resistor 38a is indicative of the photo-sensitive resisting properties of the molybdenite. The result of the alternating current flow through this starter circuit including the cathode 30, the rectifier 38b and the photo-sensitive 384 results in the application of an alternating current potential across a pair of opposed electrodes defined by the electrode and the skirt 34 of the electrode 32. The application of the alternating current potential between these closely spaced electrodes result in the ionization of the gas between these plates which ionization increases and spreads through the tube 16 until its conductivity is sufficient to permit alternating current flow through the tube 16 from the electrode 25 to the electrode 32. When the ionization reaches the levelsnfiicient to support alternating current flow through the tube between the electrodes 25 and 32, the ionized gas emits radiant energy predominately in the ultraviolet region between 1,000 and 4,000 A. Because the photo-resistive material reacts to this ultraviolet light in a manner to increase its effective resistance, the ultimate result is a substantial opening or deenergization of the starting circuit including the starting cathode 30, the conductor 42 and the photo-sensitive material 38. If the switch 15 is opened, current flow between electrodes 25, 32 ceases, the mercury vapor deionizes and the resistance of the molybdenite quickly decreases to its normal low resistance value.

FIGURE 4 is an alternative arrangement of fluorescent lamp illuminating system which may be employed with instant starting, hot-cathode fluorescent lamps, or

which may be employed with cold-cathode fluorescent lamps. In this particular embodiment both ends of the lamps 56 are provided with structural arrangements including flat ringed photo-sensitive or light reactive resistances. In this particular embodiment the generator 12 is connected through the switch 15 and the conductor 13 to a suitable electrode 52 indicated schematically on the left-hand end of the tube 50 and is connected through a conductor 14 to an electrode 54 on the right-hand end of the tube 50. A capacitor electrode 55 is positioned adjacent a skirt portion 56 of the electrode 52 and is connected to a photo-sensitive resistor 58 which has photo-resistive properties as indicated by resistor 53a and rectifying properties as indicated by the rectifier 58b, which material is connected to a corresponding resistor 60 on the opposite endwall by means of a conductor 59. As mentioned previously, conductor 59 may be either on the exterior or interior of the tube. The conductor 59 is connected to a photo-sensitive element 60 which has resistive properties as indicated by resistor 60a and also has rectifying properties as indicated by the rectifier 60b. It is to be noted that the rectifiers 58b and 60b are represented as being in series aiding polarity. It is possible, however to interchange the connections of the photo-sensitive material so that the effective rectifying properties are opposed to each other thus further decreasing the current which will flow in the starting circuit. The radiant energy sensitive material 60 is connected to a suitable capacitor electrode 64 positioned adjacent a skirt portion 65 of the electrode 54. v

The operation of the circuit of FIGURE 4 is as follows: When the switch 15 is closed the alternating current potential from the generator 12 is applied to the electrodes 56 and 65 causing alternating current to flow through the starting circuit including electrodesSS and 64, the photo-sensitive material 58 and 60 to cause ionization of the mercury vapor or other suitable gas be tween the electrodes 55, 56, and 64, 65. As this ionization increases it expands to the region between the electrodes 52, 54 such that electrical current may then be conducted between these electrodes because the now ionized path between them constitutes a lower impedance to the how of electrical current than does the impedance of the starting circuit including the starting capacitor electrodes 55, 64, and the radiant energy-sensitive resistor elements 58, 60. The radiant energy incident upon elements 58, 60 causes the effective resistance of these elements to increase until the starting circuit is effectively opened at two points thus assuring proper operation of lamp system. After the lamp is illuminated by the flow of current between the electrodes 52, 54 it may be turned off by the opening of the switch 15 thereby interrupting the current flow between the electrodes 52, 54. This interruption of current flow causes the entrapped gas to be de-ionized and the de-ionization of the gas causes the photo-sensitive elements 58, 60 to return to their low resistance state such that they are ready to again function as portions of the starting circuit in a manner previously described.

FIGURE 5a is a schematic representation of another illustrative embodiment of fluorescent light starting and operating circuit according to this invention. This embodi ment includes a lamp 70, shown in dotted outline, which may be of the hot-cathode instant-starting type. The lamp includes a pair of operating electrodes 72, '73 which are coupled to a generator 74, the latter by means of a switch 75. The lamp lamp includes a hot cathode 76, indicated schematically as a resistor, connected to the operating electrode 73. The starting circuit includes this hot cathode 76, a silicon-controlled rectifier 77, a resistor '78, a diode 80, a light actuated silicon-controlled rectifier 82, a resistor 83 and a starting capacitor electrode 84. The combination of the silicon-controlled rectifier 77, diode 80, light actuated silicon-controlled rectifier 32 and resistors 78 and 83 constitutes a normally closed switch which is opened by light incident upon the light actuated silicon-controlled rectifier 82. This normally closed switch is well known in the art and is illustrated on page 211 in FIGURE 11.4b of the General Electric SCR Manual, Third Edition. The capacitor starting electrode 84 cooperates with the skirt portion 72a of the operating electrode 72 to complete the starting circuit between electrodes 72 and 73. Thus when the switch 75 is closed, the alternating current will flow through the hot cathode 76, through the normally closed contact switch including silicon-controlled rectifier 77 and light actuated silicon-controlled rectifier 82 and through the capacitor defined by electrodes 84, through electrode 72a back to the generator 74.

When the gas within the tube 70 becomes sufliciently ionized to establish a path through the gas between the operating electrodes 72 and 73, suflicient light is emitted to actuate the light actuated silicon-controlled rectifier 82, which rectifier effectively opens the circuit of the normally closed contact between the capacitor electrode 84 and the hot cathode 76. The result will be an effective disconnecting of the start circuit and the lamp 70 will continue to operate by the operate electrodes 72 and 73, current flowing directly through the gas in the conventional manner. When the switch 75 is subsequently opened, the conduction of current through the gas between electrodes 72 and 73 will cease and the radiation incident upon the light actuated silicon-controlled rectifier 82 will also terminate. Thus the light actuated silicon-controlled rectifier 82 and the associated switch circuit will return to its normally closed condition, such that the starting circuit may again be actuated or energized by the closing of switch 75.

While three embodiments of the invention have been described in detail, it is understood that the concepts thereof could be employed in other embodiments without departing from the spirit and scope of this invention.

What is claimed is:

1. In a fluorescent lamp system the combination comprising:

a translucent tube;

endwalls on opposite ends of said tube each having a pair of conductor means extending therethrough and each sealed to said tube in fluid sealing relationship;

an operating electrode on each endwall connected to one of said conductor means;

a capacitor electrode mounted adjacent one of said operating electrodes and defining therewith a capacitor;

a photo-sensitive means connecting said capacitor electrode to the operating electrode on the other of said endwalls,

said photo-sensitive means increasing in resistance in response to light energy.

2. In a fluorescent lamp including a tube and a pair of opposed endwalls sealed to said tube in fluid sealing relationship, an operating electrode on each endwall, a start electrode positioned adjacent one of said operating electrodes to define therewith a capacitor, a light energy sensitive resistor having a positive co-efiicient of resistance and connected between said start electrode and the other of said operating electrodes.

3. The combination according to claim 2 wherein said light-sensitive resistor is comprised essentially of molybdenite.

4. A fluorescent lighting system including a translucent thereon each having an operating electrode thereon, a tube having a gas therein, a pair of opposed endwalls start electrode positioned in opposed spacial relationship to one of said operating electrodes and defining therewith the electrodes of a capacitor, a light-sensitive element connected to said start electrode and having a positive co-efiicient resistance, the other of said operating electrodes including a resistive heating element for heating the gas in said tube and conductor means connecting said heating element to said light-sensitive material.

5. A starting circuit for a fluorescent light having a pair of opposed operating electrodes comprising:

a starting electrode positioned to define a capacitor with one of said operating electrodes,

an ultraviolet ray sensitive resistor having a positive cO-efi'icient of resistance connected to said starting electrode; and

a pre-heating cathode connected to the other of said operating electrodes and to said photo-sensitive resister.

6. In a fluorescent lamp including a gas-filled tube, a pair of endwalls on opposite ends of said tube, a first and a second operating electrode, each mounted on one of said endwalls the combination comprising:

a pair of starting electrodes each positioned adjacent a different one of said operating electrodes,

a pair of light-sensitive elements each connected to one of said starting electrodes; and

conductor means connecting said light-sensitive elements.

7. In a fluorescent lamp including a gas-filled tube, a pair of endwalls on opposite ends of said tube, a first and a second operating electrode, each mounted on one of said endwalls, the combination comprising:

a starting electrode positioned on one endwall adjacent said first operating electrode; and

light actuated means coupling said start electrode to the second of said operating electrodes, said means comprising a light actuated silicon-controlled rectiher having one electrode connected to said start electrode, a diode connected to the cathode of said light actuated silicon-controlled rectifier and a silicon controlled rectifier having its gate connected to said diode and having its cathode connected to said start electrode, said last mentioned silicon-controlled rectifier having its anode connected to the other of said opera-ting electrodes, first resistor means connected between the anode of said silicon-controlled rectifier and said diode and second resistor means connected between the gate and cathode of said light actuated silicon-controlled rectifier.

8. The combination according to claim 7 further comprising a lamp cathode connected between said normally closed contact means and the second of said opera-ting electrodes.

References Cited UNITED STATES PATENTS 6/1922 Coblentz 250-21l X 12/1953 Elenbaas et a1. 3l573 DAVID J. GALVIN, Primary Examiner. 

